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I have a 4000 watt generator with a 120 volt 30 amp TT-30 R receptacle.

Can I run 120 from my gen to my panel through a single pole 30 amp breaker to just power half of my box.

I would use a TT 30 p / L5 r cord running to an L5 30 P inlet box at the house and 10/2 wire to the single pole 30 amp breaker.

An interlock switch would be used to ensure the main would be off when the gen breaker is on. All my necessary circuits are on the powered side.

Is this possible and more importantly is it safe?


Edit: Thanks so much for the response. I have re-arranged all the important circuits to the appropriate side. Instead of using the standard dual pole 30 amp breaker for the interlock I want to use the single pole for the 10/2 wire. I am assuming the interlock will work with a single pole with out issue. The panel is a 200 amp Square D Qo and there are no MWBC. This is just for occasional emergency power so very few circuits will ever be needed. Never going to use 240. I was able to run everything I needed during our last outage with a 2000 watt gen and some extension cords.

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    Most panels are not one side and the other side separated. Usually they are first on that side and the second breaker below is connected to the other side(how two breakers give 240). One side of panel will power every second breaker. That size generator good for a few lights, a TV and a toaster.
    – crip659
    Dec 8, 2021 at 19:43
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    Could we talk you into using a separate subpanel for the generator like this one?
    – JPhi1618
    Dec 8, 2021 at 19:51
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    @manassehkatz-Moving2Codidact, as long as you turn off all the 240v breakers (which ever way you do it).
    – JPhi1618
    Dec 8, 2021 at 20:33
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    @manassehkatz-Moving2Codidact That's risky as it can overload neutral if there are any MWBCs. The "turn off 240V breakers" heuristic might help, but it's not a guarantee. Not all MWBCs are on two-pole breakers: some are just two separate breakers handle-tied (and there are probably plenty out there that aren't handle-tied). Plus that's not part of the interlock so it might be forgotten in an emergency.
    – nobody
    Dec 9, 2021 at 0:15
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    You. may as well run 10/3 with a proper 30A generator inlet and wire up both phases. Your generator will only feed one phase and you'll put all your critical loads on that phase, just as you've designed. But if you ever get a larger 240V generator you can just plug it in and use it. The extra cost and effort to install it properly now is virtually zero.
    – jay613
    Dec 9, 2021 at 0:50

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As long as the interlock is there, it sounds like you're doing it legit.

It might be possible to fork or split the 120V power to feed both legs (i.e. the whole panel) but we'll need photos of how the panel internals are wired right now. We're concerned with multi-wire branch circuits (MWBC) - the existence of any, and making sure they are phased correctly as you rearrange breakers to get the loads you want on one phase. Really all MWBCs should be on 2-pole or handle-tied breakers.

Edit: Noting your additional data above, and your attestation that you have no MWBCs, I think your best bet is to use a 2-pole generator interlocked breaker, and split the incoming generator hot wire to feed both hot terminals on that 2-pole breaker. 240V loads will be inoperative. 120/240V loads will have their 120V sections work properly, so your dryer will cold-tumble clothes. You'll be able to power any 120V load in the house.

As far as using a 1-pole breaker, that depends on the particular interlock and its design. For instance the Square D QO2DTI interlock does support a 1-pole breaker, but only works on panels with smaller "back feed" main breakers. You must comply with the installation instructions of the interlock. NEC 110.3(B).

If you are forced to install a 2-pole breaker yet feel strongly about feeding only one side of the panel, feel free to connect the generator to only one of the two legs of the generator breaker.

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